Preparation and crystal structure of tetraphenylphosphonium triiodotetrabromide [PPh4][I3Br4]

Expansion of orderly stacked metakaolinite layers and order destruction using a kaolinite-tetraphenylphosphonium chloride intercalation compound

The expansion of metakaolinite layers with stacking order and the order destruction were examined by the heat treatment of a kaolinite-tetraphenylphosphonium chloride intercalation compound (Kaol-TPhPCl) at 540 °C under a nitrogen atmosphere followed by the manual grinding of the product using a mortar and a pestle. Fourier-transform infrared spectroscopy and solid-state ²⁷Al nuclear magnetic resonance spectroscopy with magic angle spinning revealed the kaolinite dehydroxylation. Moreover, the absence of kaolinite diffraction lines and the appearance of the 1.85 nm diffraction line in the X-ray diffraction pattern, together with the observation of the hexagonal plate-like morphology in the field-emission scanning electron microscopy, indicated the kaolinite amorphization with the orderly-stacked layers. These results, along with the disappearance of the 1.85 nm diffraction line upon the manual grinding of heat-treated Kaol-TPhPCl, clearly indicated the formation of expanded metakaolinite layers with stacking order and the subsequent order destruction by manual grinding.

Metakaolinite layers were expanded via the heat treatment of a kaolinite-tetraphenylphosphonium chloride intercalation compound and the obtained metakaolinite stacking order was destroyed upon manual grinding.

Rational Synthesis, Structures and Properties of the Ionic Liquid Binary Iodine-Bromine Octahalide Series [In Br8-n ]2- (n=0, 2, 3, 4)

A series of octanuclear iodine-bromine interhalides [I_n Br_8-n ]^2- (n=0, 2, 3, 4) were prepared systematically in two steps. Firstly, addition of a dihalogen (Br₂ or IBr) to the triaminocyclopropenium bromide salt [C₃ (NEt₂ )₃ ]Br forms the corresponding trihalide salt with Br₃ ^- or IBr₂ ^- anions, respectively. Secondly, addition to Br₃ ^- of half an equivalent of Br₂ gives the octabromine polyhalide [Br₈ ]^2- , whereas addition to IBr₂ ^- of half an equivalent of Br₂ , IBr or I₂ gives the corresponding interhalides: [I₂ Br₆ ]^2- , [I₃ Br₅ ]^2- , and [I₄ Br₄ ]^2- , respectively. The four octahalides were characterized by X-ray crystallography, computational studies, Raman and Far-IR spectroscopies, as well as by TGA and melting point. All of the salts were found to be ionic liquids.

Synthesis and Characterization of [Br3 ][MF6 ] (M=Sb, Ir), as well as Quantum Chemical Study of [Br3 ]+ Structure, Chemical Bonding, and Relativistic Effects Compared with [XBr2 ]+ (X=Br, I, At, Ts) and [TsZ2 ]+ (Z=F, Cl, Br, I, At, Ts)

[Br₃ ][SbF₆ ] and [Br₃ ][IrF₆ ] were synthesized by interaction of BrF₃ with Sb₂ O₃ or iridium metal, respectively. The former compound crystallizes in the orthorhombic space group Pbcn (No. 60) with a=11.9269(7), b=11.5370(7), c=12.0640(6) Å, V=1660.01(16) ų , Z=8 at 100 K. The latter compound crystallizes in the triclinic space group P 1 ‾ (No. 2) with a=5.4686(5), b=7.6861(8), c=9.9830(9) Å, α=85.320(8), β=82.060(7), γ=78.466(7)°, V=406.56(7) ų , Z=2 at 100 K. Both compounds contain the cation [Br₃ ]⁺ , which has a bent structure and is coordinated by octahedron-like anions [MF₆ ]^- (M=Sb, Ir). Experimentally obtained cell parameters, bond lengths, and angles are confirmed by solid-state DFT calculations, which differ from the experimental values by less than 2 %. Relativistic effects on the structure of the tribromonium(1+) cation are studied computationally and found to be small. For the heaviest analogues containing At and Ts, however, pronounced relativistic effects are found, which lead to a linear structure of the polyhalogen cation.

Ionic-liquid-assisted synthesis of the phosphorus interhalides [PBr4][IBr2] and [PBr4][I5Br7]

Ionic-liquid based synthesis results in the phosphorus interhalides [PBr₄][IBr₂] and [PBr₄]₂[I₅Br₇] whereof the latter shows thermal halogen release of 96.8 wt% (≤300 °C).

Electrolytes for Dye-Sensitized Solar Cells Based on Interhalogen Ionic Salts and Liquids

In this paper, we report on the preparation of interhalogen ionic liquids of the general formula [K+]XY2-, where K+=1,3-dialkylimidazolium, 1,2,3-trialkylimidazolium, or N-alkylpyridinium; XY2-=IBr2- or I2Br-. These compounds were characterized in solution and the solid state by NMR, IR, Raman, and mass spectroscopy. The crystal structure of the compound [Me2BuIm]IBr2 (7) shows that the IBr2- anion has a linear Br-I-Br structure. Indications of an equilibrium between different forms of XY2- anions in solution are observed. Interhalogen ionic salts and liquids were used as electrolyte components for encapsulated monolithic dye-sensitized solar cells. Overall light-to-electricity conversion efficiencies up to 6.4%, 5.0%, and 2.4% at 1000 W/m2 were achieved by using electrolytes based on interhalogen ionic salts and gamma-butyrolactone, glutaronitrile, or native ionic liquids as solvents, respectively. Moreover, in terms of stability, the cell performance lost 9-14% of the initial performance after 1000 h illumination at 350 W/m2.

The nature of the chemical bond in linear three-body systems: from i3- to mixed chalcogen/halogen and trichalcogen moieties

The 3 centre-4 electrons (3c-4e) and the donor/acceptor or charge-transfer models for the description of the chemical bond in linear three-body systems, such as I(3) (-) and related electron-rich (22 shell electrons) systems, are comparatively discussed on the grounds of structural data from a search of the Cambridge Structural Database (CSD). Both models account for a total bond order of 1 in these systems, and while the former fits better symmetric systems, the latter describes better strongly asymmetric situations. The 3c-4e MO scheme shows that any linear system formed by three aligned closed-shell species (24 shell electrons overall) has reason to exist provided that two electrons are removed from it to afford a 22 shell electrons three-body system: all combinations of three closed-shell halides and/or chalcogenides are considered here. A survey of the literature shows that most of these three-body systems exist. With some exceptions, their structural features vary continuously from the symmetric situation showing two equal bonds to very asymmetric situations in which one bond approaches to the value corresponding to a single bond and the second one to the sum of the van der Waals radii of the involved atoms. This indicates that the potential energy surface of these three-body systems is fairly flat, and that the chemical surrounding of the chalcogen/halogen atoms can play an important role in freezing different structural situations; this is well documented for the I(3) (-) anion. The existence of correlations between the two bond distances and more importantly the linearity observed for all these systems, independently on the degree of their asymmetry, support the state of hypervalency of the central atom.

Unprecedented Association of [Mo6Bri7YiBra6]3− Cluster Units and [MoIIIBr6]3− Complexes: Synthesis, Crystal Structures, and Properties of the Double Salts Rb3[Mo6Bri7YiBra6](Rb3[MoBr6])3 (Y=Se, Te)

The double salts Rb(3)[Mo(6)Br(i) (7)Y(i)Br(a) (6)](Rb(3)[MoBr(6)])(3) (Y=Se, Te) result from the partial disproportionation of the Mo(6)Br(12) octahedral-cluster-based bromide, in the presence of corresponding chalcogenides and RbBr salt (crystal data: Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Te(i)Br(a) (6)] (1), Pm$\bar 3$m (No. 221), a=12.1558(2) A, Z=1, R(1)=0.028; wR(2)=0.050; Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Se(i)Br(a) (6)] (2), Pm$\bar 3$m, a=12.144(3) A, Z=1, R(1)=0.028; wR(2)=0.050). The structures of 1 and 2 are built up from [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units characterised by a random distribution of seven bromine and one chalcogen ligands on all the eight inner positions that face cap the Mo(6) clusters. Such a distribution implies a static orientational disorder of the [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) units around the origin of the unit cell. Close-packed anionic layers based on [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units are stacked in the sequence ABC. This arrangement leads to very short Br(a)--Br(a) intercluster unit distances of 3.252 A, much lower than the sum of the van der Waals radii (3.70 A). The trivalent oxidation state of molybdenum in the Mo complexes and 24 valence electrons per Mo(6) cluster have been confirmed by magnetic susceptibility measurements. Salts 1 and 2 constitute the first examples of structurally characterised bromides containing discrete [Mo(III)Br(6)](3-) complexes obtained by means of solid-state synthesis.